Browsing by Autor "Christian de Muizon"

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A New Snake Skull from the Paleocene of Bolivia Sheds Light on the Evolution of Macrostomatans
(Public Library of Science, 2013) Agustín Scanferla; Hussam Zaher; Fernando E. Novas; Christian de Muizon; Ricardo Céspedes
Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.
Earliest evidence of mammalian social behaviour in the basal Tertiary of Bolivia
(Nature Portfolio, 2011) Sandrine Ladevèze; Christian de Muizon; Robin M. D. Beck; Damien Germain; Ricardo Cespedes-Paz
Late Oligocene mesotheriids (Mammalia, Notoungulata) from Salla and Lacayani (Bolivia): implications for basal mesotheriid phylogeny and distribution
(Oxford University Press, 2008) Guillaume Billet; Christian de Muizon; Bernardino Mamaní Quispe
The oldest known mesotheriids are referred to the genus Trachytherus, a taxon traditionally included in its own subfamily 'Trachytheriinae'. The ontogeny, morphological variation and systematics of the genus Trachytherus are still poorly understood and the monophyly of this taxon is questionable. For the first time, a large collection of basal mesotheriids (belonging to the genus Trachytherus) yielded by the Bolivian Salla beds (Deseadan, late Oligocene) and previously referred to T. spegazzinianus was included in a large-scale analysis. This has led to the recognition of a unique new species in the locality of Salla-Luribay, distinct from T. spegazzinianus: Trachytherus alloxus sp. nov. Skulls of this species are described and cheekteeth variation range throughout ontogeny is discussed. These new data are incorporated in a parsimony analysis of basal mesotheriids. The most probable hypothesis of a clade T. spegazzinianus-mesotheriines is discussed. The distinction of the new Salla species from the Patagonian species T. spegazzinianus confirms the faunal differences observed between these Bolivian and Patagonian Deseadan localities. Moreover, the assignment to Trachytherus spegazzinianus of mesotheriid remains from the Bolivian Lacayani deposits complicates the problem of these faunal differences. Further systematic investigations on the Lacayani fauna and on the age of the Patagonian localities are needed.
The longirostrine crocodyliforms from Bolivia and their evolution through the Cretaceous–Palaeogene boundary
(Oxford University Press, 2020) Stéphane Jouve; Christian de Muizon; Ricardo Cespedes-Paz; Víctor Sossa-Soruco; Stephane Knoll
Abstract Numerous aquatic crocodyliforms have been found during the last four decades of fieldwork in the Maastrichtian El Molino and Palaeocene Santa Lucía Formations in Bolivia. We describe new material in detail and review previously described specimens. This work enables identification of at least three new Palaeocene dyrosaurid species and the reassignement of the Maastrichtian crocodylian Dolichochampsa minima to Gavialoidea. Dolichochampsa minima is thus the oldest known South American member of this clade; previously, gavialoids were known from this continent only since the late Eocene. A new phylogenetic analysis suggests that Vectisuchus leptognathus and Elosuchus are more closely related to Dyrosauridae, and a new name, Dyrosauroidea, is proposed for this clade. Several characters previously considered as typical for dyrosaurids are present in Elosuchus. Comparison of this phylogenetic analysis with geographical and temporal distributions helps to reveal a new scenario for dyrosaurid dispersal. A high number of intercontinental interchanges occurred during the Maastrichtian, whereas higher intracontinental diversification occurred during the lower Palaeocene.
The neuroanatomy of <i>Zulmasuchus querejazus</i> (Crocodylomorpha, Sebecidae) and its implications for the paleoecology of sebecosuchians
(Wiley, 2021) Yohan Pochat‐Cottilloux; Jeremy E. Martin; Stéphane Jouve; Gwendal Perrichon; Jérôme Adrien; Céline Salaviale; Christian de Muizon; Ricardo Céspedes; Romain Amiot
The endocranial structures of the sebecid crocodylomorph Zulmasuchus querejazus (MHNC 6672) from the Lower Paleocene of Bolivia are described in this article. Using computed tomography scanning, the cranial endocast, associated nerves and arteries, endosseous labyrinths, and cranial pneumatization are reconstructed and compared with those of extant and fossil crocodylomorphs, representative of different ecomorphological adaptations. Z. querejazus exhibits an unusual flexure of the brain, pericerebral spines, semicircular canals with a narrow diameter, as well as enlarged pharyngotympanic sinuses. First, those structures allow to estimate the alert head posture and hearing capabilities of Zulmasuchus. Then, functional comparisons are proposed between this purportedly terrestrial taxon, semi-aquatic, and aquatic forms (extant crocodylians, thalattosuchians, and dyrosaurids). The narrow diameter of the semicircular canals but expanded morphology of the endosseous labyrinths and the enlarged pneumatization of the skull compared to other forms indeed tend to indicate a terrestrial lifestyle for Zulmasuchus. Our results highlight the need to gather new data, especially from altirostral forms in order to further our understanding of the evolution of endocranial structures in crocodylomorphs with different ecomorphological adaptations.
The origin of the dog-like borhyaenoid marsupials of South America
(Nature Portfolio, 1997) Christian de Muizon; Richard L. Cifelli; Ricardo Céspedes Paz